Neurologic/Head and Neck ImagingFree Access

High-Resolution Laryngeal US: Imaging Technique, Normal Anatomy, and Spectrum of Disease

Published Online:https://doi.org/10.1148/rg.2020190160

Abstract

Although US is one of the most used modalities for head and neck imaging, its use in the diagnosis of laryngeal abnormalities is much less widespread. The standard assessment of laryngeal abnormalities currently involves direct laryngoscopy and cross-sectional imaging (either CT or MRI) but rarely US. US is readily available, noninvasive, and radiation free, and it allows real-time imaging (with video for dynamic assessment), higher resolution than that of cross-sectional imaging, and the performance of targeted fine needle aspiration cytology or biopsy. This modality, particularly with the advent of high-resolution US, has been found to be at least comparable to CT or MRI for diagnosis of malignant lesions and benign abnormalities such as vocal nodules, polyps, cysts, and Reinke edema. Furthermore, it has been found to be more sensitive for diagnosis of abnormalities such as small glottic tumors, and its dynamic capability can be used to identify functional abnormalities such as vocal cord palsy. The authors outline the technique of laryngeal US, which includes strategies to avoid calcified laryngeal cartilage by imaging through the thyrohyoid and cricothyroid membranes with a five-sweep strategy supplemented by cine film of the technique. They also provide US images of common laryngeal abnormalities such as tumors with and without extralaryngeal extension; vallecular, thyroglossal, and vocal cord cysts; laryngeal mucoceles; and vocal cord palsy.

Online supplemental material is available for this article.

©RSNA, 2020

SA-CME LEARNING OBJECTIVES

After completing this journal-based SA-CME activity, participants will be able to:

  • ■ Describe the indications for laryngeal US.

  • ■ Explain the technique of laryngeal US.

  • ■ Discuss key structures and abnormalities of the larynx at US.

Introduction

US is one of the most commonly used imaging modalities for the assessment of head and neck abnormalities (1). Since the 1960s, it has been considered a possible imaging technique for the evaluation of the larynx (2). However, radiologists, even those with a subspecialty or interest in head and neck radiology, rarely use US for assessment of laryngeal abnormalities (1).

Neck US in patients with laryngeal abnormalities has been focused on laryngeal malignancy, particularly in the assessment of cervical lymph node metastases and only rarely in the determination of extension of laryngeal carcinoma into the soft tissue (35). This is due to the belief that the soft-tissue–air interface and calcified thyroid cartilage in adults preclude the visualization of laryngeal structures. However, most laryngeal structures can be assessed with US, despite the different grades of thyroid cartilage calcification (3,4,6). The thyrohyoid and cricothyroid membranes are suitable sites for the transmission of the ultrasound beam.

In current practice, laryngoscopy combined with cross-sectional imaging (CT or MRI) is the routine method for the diagnosis and assessment of most laryngeal disease (1,7). CT or MRI is used to assess the submucosal extension of laryngeal lesions and the tumoral invasion of intra- and extralaryngeal structures, because laryngoscopy alone does not allow delineation of these features (3,5). These techniques offer high accuracy for pretherapeutic staging; the accuracy of MRI has been reported as 87.5% and that of CT as 86% (3,8,9). The accuracy of US is comparable to those of CT and MRI in pretherapeutic staging. In one study (3), the accuracy of pretherapeutic staging of laryngeal cancer with US was 83.3%, whereas the accuracy with CT was 88.8%. A further study (10) found 80% accuracy for staging of glottic carcinoma with US, compared with 76.7% with MRI. Furthermore, US affords much higher-resolution imaging than either CT or MRI and can, therefore, allow identification of laryngeal anatomy and subtle but clinically important abnormalities that are not clearly visible with other modalities. US has been shown to be more valuable than CT for detection of benign lesions such as vocal cord nodules, polyps, and cysts, and in depicting Reinke edema (5).

US offers advantages such as its common availability, noninvasiveness, lack of radiation, and ability to allow real-time imaging (with video for dynamic assessment) and to provide higher resolution than that of cross-sectional imaging. Most of all, it is suitable for patients who, because of irritating laryngeal abnormalities, have difficulty keeping still during the performance of CT and MRI. Moreover, it is safe during pregnancy and for children, in whom it is widely applied, particularly in the subglottis, for diagnosis of stenosis and hemangiomas (11) and may be combined with guided fine-needle aspiration or biopsy. The real-time nature of US acquisition allows assessment of laryngeal function.

This article outlines our technique of laryngeal US, highlighting the anatomy that is now visible with high-resolution US, some of which is, to our knowledge, previously undescribed in the medical literature. Malignant and benign laryngeal diseases are described, including the use of US in staging and the US appearances of laryngoceles, laryngeal cysts, postradiation therapy change, dynamic assessment, and vocal cord function. In addition we explain techniques to identify the positions and complications of tracheal stents. We also demonstrate both the pertinent anatomy for laryngeal US and why US should be considered a powerful imaging modality for the diagnosis of different laryngeal pathologic processes (35,1217).

Laryngeal Anatomy and US Technique

The examination of the larynx should be performed with high-frequency (7–18 MHz) linear and sector (6.5–8 MHz) transducers (the latter for assessment of the base of the tongue and the preepiglottic space) to obtain high-resolution images (both static and video images). Routine US of the larynx should include midline transverse, paramedian transverse, and longitudinal views (or sweeps) obtained with the patient in the supine position, although a seated position may also be used in patients who are having trouble breathing.

First Sweep

In the midline transverse plane, scan from superior to inferior, starting just above the hyoid bone with the patient’s chin up (Movie 1). The hyoid bone is the first structure that should be identified (ie, the body and junction, with greater and lesser horns, and the associated acoustic shadow should be determined) (Fig 1a). Next, angle the probe superiorly to assess the intrinsic muscles of the base of the tongue, including the more superficial lingual tonsils (ie, to assess their symmetry, depth, and whether the normal tonsillar folds are present). Then angle the probe inferiorly to image the valleculae. Depending on the angle of the probe, the hyperechoic line of air lining the mucosa may represent the anterior wall (most frequently), the floor, or the posterior wall of the valleculae. Look for the midline glossoepiglottic fold and the vallecular floor just superior to the preepiglottic fat (Fig 1b).

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Movie 1. Cine images from laryngeal US show the first sweep in the transverse plane from superior to inferior.

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, with corresponding illustrations (right) of the anatomic                         orientation. (a) US image shows the hyoid bone, which appears as a bright                         line with a prominent acoustic shadow (+). (b) US image at the level of                         the floor of the vallecula (*) shows the posterior surface of the                         vallecula as a bright line (solid arrows). The median glossoepiglottic folds                         can also be seen in this view (dashed arrow). (c) US image at the level of                         the thyrohyoid membrane (dashed arrows) shows the preepiglottic space                         (*), which is limited anteriorly by the thyrohyoid membrane (dashed                         arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH)                         muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US                         image at the level of the thyroid notch shows the continuity between the                         preepiglottic space (*, curved arrows) and the paraglottic space                         (+, curved arrows). Also visible are the thyroid cartilage (dashed                         lines) and the inferior aspect of the epiglottis (straight                         arrow).

Figure 1a. Midline transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the hyoid bone, which appears as a bright line with a prominent acoustic shadow (+). (b) US image at the level of the floor of the vallecula (*) shows the posterior surface of the vallecula as a bright line (solid arrows). The median glossoepiglottic folds can also be seen in this view (dashed arrow). (c) US image at the level of the thyrohyoid membrane (dashed arrows) shows the preepiglottic space (*), which is limited anteriorly by the thyrohyoid membrane (dashed arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH) muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US image at the level of the thyroid notch shows the continuity between the preepiglottic space (*, curved arrows) and the paraglottic space (+, curved arrows). Also visible are the thyroid cartilage (dashed lines) and the inferior aspect of the epiglottis (straight arrow).

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, with corresponding illustrations (right) of the anatomic                         orientation. (a) US image shows the hyoid bone, which appears as a bright                         line with a prominent acoustic shadow (+). (b) US image at the level of                         the floor of the vallecula (*) shows the posterior surface of the                         vallecula as a bright line (solid arrows). The median glossoepiglottic folds                         can also be seen in this view (dashed arrow). (c) US image at the level of                         the thyrohyoid membrane (dashed arrows) shows the preepiglottic space                         (*), which is limited anteriorly by the thyrohyoid membrane (dashed                         arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH)                         muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US                         image at the level of the thyroid notch shows the continuity between the                         preepiglottic space (*, curved arrows) and the paraglottic space                         (+, curved arrows). Also visible are the thyroid cartilage (dashed                         lines) and the inferior aspect of the epiglottis (straight                         arrow).

Figure 1b. Midline transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the hyoid bone, which appears as a bright line with a prominent acoustic shadow (+). (b) US image at the level of the floor of the vallecula (*) shows the posterior surface of the vallecula as a bright line (solid arrows). The median glossoepiglottic folds can also be seen in this view (dashed arrow). (c) US image at the level of the thyrohyoid membrane (dashed arrows) shows the preepiglottic space (*), which is limited anteriorly by the thyrohyoid membrane (dashed arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH) muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US image at the level of the thyroid notch shows the continuity between the preepiglottic space (*, curved arrows) and the paraglottic space (+, curved arrows). Also visible are the thyroid cartilage (dashed lines) and the inferior aspect of the epiglottis (straight arrow).

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, with corresponding illustrations (right) of the anatomic                         orientation. (a) US image shows the hyoid bone, which appears as a bright                         line with a prominent acoustic shadow (+). (b) US image at the level of                         the floor of the vallecula (*) shows the posterior surface of the                         vallecula as a bright line (solid arrows). The median glossoepiglottic folds                         can also be seen in this view (dashed arrow). (c) US image at the level of                         the thyrohyoid membrane (dashed arrows) shows the preepiglottic space                         (*), which is limited anteriorly by the thyrohyoid membrane (dashed                         arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH)                         muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US                         image at the level of the thyroid notch shows the continuity between the                         preepiglottic space (*, curved arrows) and the paraglottic space                         (+, curved arrows). Also visible are the thyroid cartilage (dashed                         lines) and the inferior aspect of the epiglottis (straight                         arrow).

Figure 1c. Midline transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the hyoid bone, which appears as a bright line with a prominent acoustic shadow (+). (b) US image at the level of the floor of the vallecula (*) shows the posterior surface of the vallecula as a bright line (solid arrows). The median glossoepiglottic folds can also be seen in this view (dashed arrow). (c) US image at the level of the thyrohyoid membrane (dashed arrows) shows the preepiglottic space (*), which is limited anteriorly by the thyrohyoid membrane (dashed arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH) muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US image at the level of the thyroid notch shows the continuity between the preepiglottic space (*, curved arrows) and the paraglottic space (+, curved arrows). Also visible are the thyroid cartilage (dashed lines) and the inferior aspect of the epiglottis (straight arrow).

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, with corresponding illustrations (right) of the anatomic                         orientation. (a) US image shows the hyoid bone, which appears as a bright                         line with a prominent acoustic shadow (+). (b) US image at the level of                         the floor of the vallecula (*) shows the posterior surface of the                         vallecula as a bright line (solid arrows). The median glossoepiglottic folds                         can also be seen in this view (dashed arrow). (c) US image at the level of                         the thyrohyoid membrane (dashed arrows) shows the preepiglottic space                         (*), which is limited anteriorly by the thyrohyoid membrane (dashed                         arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH)                         muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US                         image at the level of the thyroid notch shows the continuity between the                         preepiglottic space (*, curved arrows) and the paraglottic space                         (+, curved arrows). Also visible are the thyroid cartilage (dashed                         lines) and the inferior aspect of the epiglottis (straight                         arrow).

Figure 1d. Midline transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the hyoid bone, which appears as a bright line with a prominent acoustic shadow (+). (b) US image at the level of the floor of the vallecula (*) shows the posterior surface of the vallecula as a bright line (solid arrows). The median glossoepiglottic folds can also be seen in this view (dashed arrow). (c) US image at the level of the thyrohyoid membrane (dashed arrows) shows the preepiglottic space (*), which is limited anteriorly by the thyrohyoid membrane (dashed arrows) and the more superficial thyrohyoid (TH) and sternohyoid (SH) muscles, and posteriorly by the hypoechoic epiglottis (solid arrows). (d) US image at the level of the thyroid notch shows the continuity between the preepiglottic space (*, curved arrows) and the paraglottic space (+, curved arrows). Also visible are the thyroid cartilage (dashed lines) and the inferior aspect of the epiglottis (straight arrow).

Sweep the probe inferiorly over the thyrohyoid membrane (Fig 1c) to the superior thyroid notch to assess the infrahyoid epiglottis and, anterior to this, the superior aspect of the preepiglottic and paraglottic spaces. Note that the preepiglottic and paraglottic spaces contain fat and communicate anteriorly (Fig 1c, 1d).

Make use of the US “window” of the superior thyroid notch (ie, the Adam’s apple) by angling the probe inferiorly at this site, avoiding the thyroid cartilage, so that even when the laminae are heavily calcified, most of the more inferior pre-and paraglottic spaces and the infrahyoid epiglottis can be visualized (Fig 1d).

If the thyroid cartilage is not ossified, the supraglottic and glottic anatomy (ie, the anterior commissure region, the vocalis and thyroarytenoid muscles, the arytenoid cartilage, the combined transverse and oblique interarytenoid muscles, the posterior cricoarytenoid muscles, and the thyropharyngeal component of the inferior constrictor) are displayed by placing the probe directly over the cartilage (Fig 2a2c). The cricothyroid muscle is visible outside of the cricothyroid membrane. If the thyroid cartilage is calcified, angle the probe superiorly in the cricothyroid window region to also assess the inferior supraglottis and glottis. However, except for the interarytenoid muscles, the supraglottic and glottic structures are usually more clearly delineated in sweeps 2 and 3. Movie 2 shows normal vocal cord movement in a transverse plane.

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, and corresponding illustrations (right) of the anatomic                         orientation. (a) US image at the level of the cricothyroid and inferior                         thyroid laminae (dashed lines) shows the vocal cords in adduction (*).                         The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the                         right, and the interarytenoid muscles (solid arrows) are seen posteriorly.                         Because of the superior angulation of the probe, the hypoechoic vocal cords                         (*) and the anterior commissure (+) are visible anteriorly, as are                         the hyperechoic false vocal cords posteriorly. (b, c) US images of the                         transverse right (b) and left (c) planes at the level of the cricoid                         cartilage (curved line). The cricothyroid muscle (dotted line) and the                         posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH)                         and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal                         component of the inferior constrictor (solid arrows) and of the air and                         mucosal interface (dashed arrows in b) of the anterior cricothyroid region.                         The noncalcified inferior horn of the left thyroid cartilage (* in c)                         is also visible.

Figure 2a. Midline transverse plane US images (left) of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the cricothyroid and inferior thyroid laminae (dashed lines) shows the vocal cords in adduction (*). The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the right, and the interarytenoid muscles (solid arrows) are seen posteriorly. Because of the superior angulation of the probe, the hypoechoic vocal cords (*) and the anterior commissure (+) are visible anteriorly, as are the hyperechoic false vocal cords posteriorly. (b, c) US images of the transverse right (b) and left (c) planes at the level of the cricoid cartilage (curved line). The cricothyroid muscle (dotted line) and the posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH) and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal component of the inferior constrictor (solid arrows) and of the air and mucosal interface (dashed arrows in b) of the anterior cricothyroid region. The noncalcified inferior horn of the left thyroid cartilage (* in c) is also visible.

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, and corresponding illustrations (right) of the anatomic                         orientation. (a) US image at the level of the cricothyroid and inferior                         thyroid laminae (dashed lines) shows the vocal cords in adduction (*).                         The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the                         right, and the interarytenoid muscles (solid arrows) are seen posteriorly.                         Because of the superior angulation of the probe, the hypoechoic vocal cords                         (*) and the anterior commissure (+) are visible anteriorly, as are                         the hyperechoic false vocal cords posteriorly. (b, c) US images of the                         transverse right (b) and left (c) planes at the level of the cricoid                         cartilage (curved line). The cricothyroid muscle (dotted line) and the                         posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH)                         and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal                         component of the inferior constrictor (solid arrows) and of the air and                         mucosal interface (dashed arrows in b) of the anterior cricothyroid region.                         The noncalcified inferior horn of the left thyroid cartilage (* in c)                         is also visible.

Figure 2b. Midline transverse plane US images (left) of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the cricothyroid and inferior thyroid laminae (dashed lines) shows the vocal cords in adduction (*). The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the right, and the interarytenoid muscles (solid arrows) are seen posteriorly. Because of the superior angulation of the probe, the hypoechoic vocal cords (*) and the anterior commissure (+) are visible anteriorly, as are the hyperechoic false vocal cords posteriorly. (b, c) US images of the transverse right (b) and left (c) planes at the level of the cricoid cartilage (curved line). The cricothyroid muscle (dotted line) and the posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH) and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal component of the inferior constrictor (solid arrows) and of the air and mucosal interface (dashed arrows in b) of the anterior cricothyroid region. The noncalcified inferior horn of the left thyroid cartilage (* in c) is also visible.

Midline transverse plane US images (left) of the larynx, from superior                         to inferior, and corresponding illustrations (right) of the anatomic                         orientation. (a) US image at the level of the cricothyroid and inferior                         thyroid laminae (dashed lines) shows the vocal cords in adduction (*).                         The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the                         right, and the interarytenoid muscles (solid arrows) are seen posteriorly.                         Because of the superior angulation of the probe, the hypoechoic vocal cords                         (*) and the anterior commissure (+) are visible anteriorly, as are                         the hyperechoic false vocal cords posteriorly. (b, c) US images of the                         transverse right (b) and left (c) planes at the level of the cricoid                         cartilage (curved line). The cricothyroid muscle (dotted line) and the                         posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH)                         and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal                         component of the inferior constrictor (solid arrows) and of the air and                         mucosal interface (dashed arrows in b) of the anterior cricothyroid region.                         The noncalcified inferior horn of the left thyroid cartilage (* in c)                         is also visible.

Figure 2c. Midline transverse plane US images (left) of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the cricothyroid and inferior thyroid laminae (dashed lines) shows the vocal cords in adduction (*). The apposed arytenoid cartilage (dotted arrows) are partly echogenic on the right, and the interarytenoid muscles (solid arrows) are seen posteriorly. Because of the superior angulation of the probe, the hypoechoic vocal cords (*) and the anterior commissure (+) are visible anteriorly, as are the hyperechoic false vocal cords posteriorly. (b, c) US images of the transverse right (b) and left (c) planes at the level of the cricoid cartilage (curved line). The cricothyroid muscle (dotted line) and the posterior cricoarytenoid muscle (PCA) can be seen. Note the sternohyoid (SH) and sternothyroid (ST) strap muscles anteriorly, and the thyropharyngeal component of the inferior constrictor (solid arrows) and of the air and mucosal interface (dashed arrows in b) of the anterior cricothyroid region. The noncalcified inferior horn of the left thyroid cartilage (* in c) is also visible.

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Movie 2. Cine images from laryngeal US show normal vocal cord movement in the transverse plane.

From the cricothyroid region, sweep the probe inferiorly to assess the cricoid cartilage and the proximal tracheal rings. At the level of the cricoid cartilage, the sternohyoid, sternothyroid, cricothyroid, posterior cricoarytenoid, and thyropharyngeus muscles can be visualized (Fig 2b, 2c). The cricothyroid muscle is the only laryngeal muscle that is not innervated by the recurrent laryngeal nerve but instead by the external branch of the superior laryngeal nerve. No hypoechoic soft tissue should be visible deep to the cricothyroid membrane; if it is present, it usually represents a subglottic abnormality such as subglottic tumor extension. Only the bright line of the air–soft tissue interface of the anterior wall of the cricothyroid junction should be visible, and anterior to it, a layer of hyperechoic fatty tissue should be seen (Fig 2b). Finally, prelaryngeal (delphian) (level VI) nodes are clearly visible, even when they are small (2 mm), and should be assessed during this initial sweep.

Second and Third (Right and Left Transverse Paramedian) Sweeps

The next step is to scan in the right and left transverse paramedian positions. By sweeping from superior to inferior, first identify the faucial tonsils and overlying constrictor, the lateral aspect of the vallecula, the lateral tongue base, and the glosso-tonsillar sulcus (Fig 3a; Movies 3, 4).

Left paramedian transverse plane US images (left) of the larynx, from                         superior to inferior, with corresponding illustrations (right) of the                         anatomic orientation. (a) US image shows the tongue base (TB),                         glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor                         muscles (solid arrows). (b, c) Color Doppler US images at the level of the                         superior paraglottis show the superior laryngeal vessels perforating the                         thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*).                         Note the presence of air in the piriform sinus (oval outline in c), the                         thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the                         thyrohyoid muscle (TH).

Figure 3a. Left paramedian transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the tongue base (TB), glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor muscles (solid arrows). (b, c) Color Doppler US images at the level of the superior paraglottis show the superior laryngeal vessels perforating the thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*). Note the presence of air in the piriform sinus (oval outline in c), the thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the thyrohyoid muscle (TH).

Left paramedian transverse plane US images (left) of the larynx, from                         superior to inferior, with corresponding illustrations (right) of the                         anatomic orientation. (a) US image shows the tongue base (TB),                         glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor                         muscles (solid arrows). (b, c) Color Doppler US images at the level of the                         superior paraglottis show the superior laryngeal vessels perforating the                         thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*).                         Note the presence of air in the piriform sinus (oval outline in c), the                         thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the                         thyrohyoid muscle (TH).

Figure 3b. Left paramedian transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the tongue base (TB), glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor muscles (solid arrows). (b, c) Color Doppler US images at the level of the superior paraglottis show the superior laryngeal vessels perforating the thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*). Note the presence of air in the piriform sinus (oval outline in c), the thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the thyrohyoid muscle (TH).

Left paramedian transverse plane US images (left) of the larynx, from                         superior to inferior, with corresponding illustrations (right) of the                         anatomic orientation. (a) US image shows the tongue base (TB),                         glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor                         muscles (solid arrows). (b, c) Color Doppler US images at the level of the                         superior paraglottis show the superior laryngeal vessels perforating the                         thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*).                         Note the presence of air in the piriform sinus (oval outline in c), the                         thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the                         thyrohyoid muscle (TH).

Figure 3c. Left paramedian transverse plane US images (left) of the larynx, from superior to inferior, with corresponding illustrations (right) of the anatomic orientation. (a) US image shows the tongue base (TB), glossotonsillar sulcus (dashed arrow), faucial tonsil (T), and constrictor muscles (solid arrows). (b, c) Color Doppler US images at the level of the superior paraglottis show the superior laryngeal vessels perforating the thyrohyoid membrane (arrow) inferiorly in the paraglottic space (*). Note the presence of air in the piriform sinus (oval outline in c), the thyroid cartilage (dashed line), the sternohyoid muscle (SH), and the thyrohyoid muscle (TH).

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Movie 3. Cine images from laryngeal US show the second sweep (the right transverse paramedian sweep).

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Movie 4. Cine images from laryngeal US show the third sweep (the left transverse paramedian sweep).

As in the first midline sweep, identify the thyrohyoid membrane (Fig 1c) and then identify the neurovascular pedicle comprising the superior laryngeal vessels and the internal branch of the superior laryngeal nerve (Fig 3b, 3c), confirming with color Doppler US. Note the thyroid cartilage with the thyrohyoid muscle and sternohyoid muscles just external to it (Fig 3b, 3c).

Assess the thyroid cartilage, both the laminae and the superior and inferior horns. Deep to the thyroid lamina, identify the inferior pathway of the superior laryngeal vessels and the internal laryngeal nerve, the paraglottic fat of the supraglottis, the superior slip of the thyroarytenoid muscle (Fig 4a) (which, more inferiorly, forms the bulk of true vocal cord) (Fig 4b), the more posterior piriform apex (Fig 4c), and the surrounding inferior constrictor muscle.

Left paramedian transverse plane US images of the larynx, from                         superior to inferior, and corresponding illustrations (right) of the                         anatomic orientation. (a) US image at the level of the false vocal cord                         (*) shows the superior slip of the thyroarytenoid muscle (dotted                         arrows) and the thyroid lamina (dashed line). (b) US image at the level of                         the hypoechoic true vocal cords shows the more medial vocalis muscle (solid                         arrows), which is separated from the larger more lateral thyroarytenoid                         muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the                         thyroarytenoid muscle, which is separated from the thyroid lamina (dashed                         arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed                         line indicates the cartilage of the thyroid lamina. Note the presence of                         nonossified arytenoid cartilage (+). (c) US image acquired at a level                         just posterior to that in b shows the thyropharyngeus (TP), piriform apex                         (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid                         lamina (dashed line).

Figure 4a. Left paramedian transverse plane US images of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the false vocal cord (*) shows the superior slip of the thyroarytenoid muscle (dotted arrows) and the thyroid lamina (dashed line). (b) US image at the level of the hypoechoic true vocal cords shows the more medial vocalis muscle (solid arrows), which is separated from the larger more lateral thyroarytenoid muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the thyroarytenoid muscle, which is separated from the thyroid lamina (dashed arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed line indicates the cartilage of the thyroid lamina. Note the presence of nonossified arytenoid cartilage (+). (c) US image acquired at a level just posterior to that in b shows the thyropharyngeus (TP), piriform apex (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid lamina (dashed line).

Left paramedian transverse plane US images of the larynx, from                         superior to inferior, and corresponding illustrations (right) of the                         anatomic orientation. (a) US image at the level of the false vocal cord                         (*) shows the superior slip of the thyroarytenoid muscle (dotted                         arrows) and the thyroid lamina (dashed line). (b) US image at the level of                         the hypoechoic true vocal cords shows the more medial vocalis muscle (solid                         arrows), which is separated from the larger more lateral thyroarytenoid                         muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the                         thyroarytenoid muscle, which is separated from the thyroid lamina (dashed                         arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed                         line indicates the cartilage of the thyroid lamina. Note the presence of                         nonossified arytenoid cartilage (+). (c) US image acquired at a level                         just posterior to that in b shows the thyropharyngeus (TP), piriform apex                         (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid                         lamina (dashed line).

Figure 4b. Left paramedian transverse plane US images of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the false vocal cord (*) shows the superior slip of the thyroarytenoid muscle (dotted arrows) and the thyroid lamina (dashed line). (b) US image at the level of the hypoechoic true vocal cords shows the more medial vocalis muscle (solid arrows), which is separated from the larger more lateral thyroarytenoid muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the thyroarytenoid muscle, which is separated from the thyroid lamina (dashed arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed line indicates the cartilage of the thyroid lamina. Note the presence of nonossified arytenoid cartilage (+). (c) US image acquired at a level just posterior to that in b shows the thyropharyngeus (TP), piriform apex (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid lamina (dashed line).

Left paramedian transverse plane US images of the larynx, from                         superior to inferior, and corresponding illustrations (right) of the                         anatomic orientation. (a) US image at the level of the false vocal cord                         (*) shows the superior slip of the thyroarytenoid muscle (dotted                         arrows) and the thyroid lamina (dashed line). (b) US image at the level of                         the hypoechoic true vocal cords shows the more medial vocalis muscle (solid                         arrows), which is separated from the larger more lateral thyroarytenoid                         muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the                         thyroarytenoid muscle, which is separated from the thyroid lamina (dashed                         arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed                         line indicates the cartilage of the thyroid lamina. Note the presence of                         nonossified arytenoid cartilage (+). (c) US image acquired at a level                         just posterior to that in b shows the thyropharyngeus (TP), piriform apex                         (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid                         lamina (dashed line).

Figure 4c. Left paramedian transverse plane US images of the larynx, from superior to inferior, and corresponding illustrations (right) of the anatomic orientation. (a) US image at the level of the false vocal cord (*) shows the superior slip of the thyroarytenoid muscle (dotted arrows) and the thyroid lamina (dashed line). (b) US image at the level of the hypoechoic true vocal cords shows the more medial vocalis muscle (solid arrows), which is separated from the larger more lateral thyroarytenoid muscle (TA) by a thin hyperechoic line (broadly spaced dashed line) and the thyroarytenoid muscle, which is separated from the thyroid lamina (dashed arrows) by a thin rim of hyperechoic paraglottic fat. Narrowly spaced dashed line indicates the cartilage of the thyroid lamina. Note the presence of nonossified arytenoid cartilage (+). (c) US image acquired at a level just posterior to that in b shows the thyropharyngeus (TP), piriform apex (P), interarytenoid muscles (IA), arytenoid cartilage (+), and thyroid lamina (dashed line).

The true vocal cord is hypoechoic and is composed of the vocal ligament and vocalis muscle medially and the bulkier thyroarytenoid muscle laterally. The two muscles may be distinguished at US by the fine hyperechoic line separating them (Fig 4b). Also note a second fine hyperechoic line separating the lateral aspect of the thyroarytenoid muscle from the overlying thyroid lamina (Fig 4a4c), which may not be visible in patients with glottic carcinoma.

At this level, identify the arytenoid cartilage, which has a variable appearance and is usually echogenic due to calcification in older patients but tends to be hypoechoic in young patients (Fig 4b). The “hockey stick” appearance of the arytenoid cartilage is seen in the transverse plane. The vocal process, which resembles the handle of the stick, extends anteriorly along the medial true cord (vocalis muscle and ligament) and can be clearly identified, as can the muscular (ie, lateral) process (Fig 4b, 4c). The apex (ie, superior aspect) of the cartilage is better seen in the subsequent longitudinal US sweep than in the transverse paramedian sweeps (Fig 5a).

Right parasagittal plane images of the larynx, from posterior to                         anterior, with illustrations (right) of the corresponding anatomic                         orientation. (a) US image shows the cricoid cartilage (curved line); the                         thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior                         slip (solid arrows); the arytenoid cartilage (+), which almost mirrors                         it with its concave surface (fovea) for attachment of the thyroarytenoid                         muscle (curved dotted line); and the apex (dashed arrow), extending                         superiorly. (b) US image shows the false vocal cord (solid straight arrow),                         a thickened laryngeal ventricle (*), and the true vocal cord (dashed                         arrow). Note the paraglottic space (curved arrow), extending between the                         ventricle and the overlying thyroid lamina (dashed line), which is a                         submucosal route for supraglottic extension of glottic tumors and is not                         visible at endoscopy; the cricothyroid membrane (+); and the anterior                         cricoid cartilage (curved line). (c) Color Doppler US image shows the                         cricothyroid artery perforating the cricothyroid membrane. Note the                         laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle                         (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage                         (curved line). (d) Midline sagittal plane US image in the thyrohyoid region                         shows the hyoid bone (oval outline), the superior aspect of the thyroid                         lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted                         arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat                         (*), and the hypoechoic epiglottic cartilage (solid arrows).

Figure 5a. Right parasagittal plane images of the larynx, from posterior to anterior, with illustrations (right) of the corresponding anatomic orientation. (a) US image shows the cricoid cartilage (curved line); the thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior slip (solid arrows); the arytenoid cartilage (+), which almost mirrors it with its concave surface (fovea) for attachment of the thyroarytenoid muscle (curved dotted line); and the apex (dashed arrow), extending superiorly. (b) US image shows the false vocal cord (solid straight arrow), a thickened laryngeal ventricle (*), and the true vocal cord (dashed arrow). Note the paraglottic space (curved arrow), extending between the ventricle and the overlying thyroid lamina (dashed line), which is a submucosal route for supraglottic extension of glottic tumors and is not visible at endoscopy; the cricothyroid membrane (+); and the anterior cricoid cartilage (curved line). (c) Color Doppler US image shows the cricothyroid artery perforating the cricothyroid membrane. Note the laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage (curved line). (d) Midline sagittal plane US image in the thyrohyoid region shows the hyoid bone (oval outline), the superior aspect of the thyroid lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat (*), and the hypoechoic epiglottic cartilage (solid arrows).

Right parasagittal plane images of the larynx, from posterior to                         anterior, with illustrations (right) of the corresponding anatomic                         orientation. (a) US image shows the cricoid cartilage (curved line); the                         thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior                         slip (solid arrows); the arytenoid cartilage (+), which almost mirrors                         it with its concave surface (fovea) for attachment of the thyroarytenoid                         muscle (curved dotted line); and the apex (dashed arrow), extending                         superiorly. (b) US image shows the false vocal cord (solid straight arrow),                         a thickened laryngeal ventricle (*), and the true vocal cord (dashed                         arrow). Note the paraglottic space (curved arrow), extending between the                         ventricle and the overlying thyroid lamina (dashed line), which is a                         submucosal route for supraglottic extension of glottic tumors and is not                         visible at endoscopy; the cricothyroid membrane (+); and the anterior                         cricoid cartilage (curved line). (c) Color Doppler US image shows the                         cricothyroid artery perforating the cricothyroid membrane. Note the                         laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle                         (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage                         (curved line). (d) Midline sagittal plane US image in the thyrohyoid region                         shows the hyoid bone (oval outline), the superior aspect of the thyroid                         lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted                         arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat                         (*), and the hypoechoic epiglottic cartilage (solid arrows).

Figure 5b. Right parasagittal plane images of the larynx, from posterior to anterior, with illustrations (right) of the corresponding anatomic orientation. (a) US image shows the cricoid cartilage (curved line); the thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior slip (solid arrows); the arytenoid cartilage (+), which almost mirrors it with its concave surface (fovea) for attachment of the thyroarytenoid muscle (curved dotted line); and the apex (dashed arrow), extending superiorly. (b) US image shows the false vocal cord (solid straight arrow), a thickened laryngeal ventricle (*), and the true vocal cord (dashed arrow). Note the paraglottic space (curved arrow), extending between the ventricle and the overlying thyroid lamina (dashed line), which is a submucosal route for supraglottic extension of glottic tumors and is not visible at endoscopy; the cricothyroid membrane (+); and the anterior cricoid cartilage (curved line). (c) Color Doppler US image shows the cricothyroid artery perforating the cricothyroid membrane. Note the laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage (curved line). (d) Midline sagittal plane US image in the thyrohyoid region shows the hyoid bone (oval outline), the superior aspect of the thyroid lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat (*), and the hypoechoic epiglottic cartilage (solid arrows).

Right parasagittal plane images of the larynx, from posterior to                         anterior, with illustrations (right) of the corresponding anatomic                         orientation. (a) US image shows the cricoid cartilage (curved line); the                         thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior                         slip (solid arrows); the arytenoid cartilage (+), which almost mirrors                         it with its concave surface (fovea) for attachment of the thyroarytenoid                         muscle (curved dotted line); and the apex (dashed arrow), extending                         superiorly. (b) US image shows the false vocal cord (solid straight arrow),                         a thickened laryngeal ventricle (*), and the true vocal cord (dashed                         arrow). Note the paraglottic space (curved arrow), extending between the                         ventricle and the overlying thyroid lamina (dashed line), which is a                         submucosal route for supraglottic extension of glottic tumors and is not                         visible at endoscopy; the cricothyroid membrane (+); and the anterior                         cricoid cartilage (curved line). (c) Color Doppler US image shows the                         cricothyroid artery perforating the cricothyroid membrane. Note the                         laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle                         (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage                         (curved line). (d) Midline sagittal plane US image in the thyrohyoid region                         shows the hyoid bone (oval outline), the superior aspect of the thyroid                         lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted                         arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat                         (*), and the hypoechoic epiglottic cartilage (solid arrows).

Figure 5c. Right parasagittal plane images of the larynx, from posterior to anterior, with illustrations (right) of the corresponding anatomic orientation. (a) US image shows the cricoid cartilage (curved line); the thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior slip (solid arrows); the arytenoid cartilage (+), which almost mirrors it with its concave surface (fovea) for attachment of the thyroarytenoid muscle (curved dotted line); and the apex (dashed arrow), extending superiorly. (b) US image shows the false vocal cord (solid straight arrow), a thickened laryngeal ventricle (*), and the true vocal cord (dashed arrow). Note the paraglottic space (curved arrow), extending between the ventricle and the overlying thyroid lamina (dashed line), which is a submucosal route for supraglottic extension of glottic tumors and is not visible at endoscopy; the cricothyroid membrane (+); and the anterior cricoid cartilage (curved line). (c) Color Doppler US image shows the cricothyroid artery perforating the cricothyroid membrane. Note the laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage (curved line). (d) Midline sagittal plane US image in the thyrohyoid region shows the hyoid bone (oval outline), the superior aspect of the thyroid lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat (*), and the hypoechoic epiglottic cartilage (solid arrows).

Right parasagittal plane images of the larynx, from posterior to                         anterior, with illustrations (right) of the corresponding anatomic                         orientation. (a) US image shows the cricoid cartilage (curved line); the                         thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior                         slip (solid arrows); the arytenoid cartilage (+), which almost mirrors                         it with its concave surface (fovea) for attachment of the thyroarytenoid                         muscle (curved dotted line); and the apex (dashed arrow), extending                         superiorly. (b) US image shows the false vocal cord (solid straight arrow),                         a thickened laryngeal ventricle (*), and the true vocal cord (dashed                         arrow). Note the paraglottic space (curved arrow), extending between the                         ventricle and the overlying thyroid lamina (dashed line), which is a                         submucosal route for supraglottic extension of glottic tumors and is not                         visible at endoscopy; the cricothyroid membrane (+); and the anterior                         cricoid cartilage (curved line). (c) Color Doppler US image shows the                         cricothyroid artery perforating the cricothyroid membrane. Note the                         laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle                         (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage                         (curved line). (d) Midline sagittal plane US image in the thyrohyoid region                         shows the hyoid bone (oval outline), the superior aspect of the thyroid                         lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted                         arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat                         (*), and the hypoechoic epiglottic cartilage (solid arrows).

Figure 5d. Right parasagittal plane images of the larynx, from posterior to anterior, with illustrations (right) of the corresponding anatomic orientation. (a) US image shows the cricoid cartilage (curved line); the thyroid lamina (dashed line), the thyroarytenoid muscle, with its superior slip (solid arrows); the arytenoid cartilage (+), which almost mirrors it with its concave surface (fovea) for attachment of the thyroarytenoid muscle (curved dotted line); and the apex (dashed arrow), extending superiorly. (b) US image shows the false vocal cord (solid straight arrow), a thickened laryngeal ventricle (*), and the true vocal cord (dashed arrow). Note the paraglottic space (curved arrow), extending between the ventricle and the overlying thyroid lamina (dashed line), which is a submucosal route for supraglottic extension of glottic tumors and is not visible at endoscopy; the cricothyroid membrane (+); and the anterior cricoid cartilage (curved line). (c) Color Doppler US image shows the cricothyroid artery perforating the cricothyroid membrane. Note the laryngeal ventricle (*), the superior slip of the thyroarytenoid muscle (arrows), the thyroid cartilage (dashed line), and the cricoid cartilage (curved line). (d) Midline sagittal plane US image in the thyrohyoid region shows the hyoid bone (oval outline), the superior aspect of the thyroid lamina (dashed line), the petiole (☆), the thyrohyoid muscle (dotted arrow), the thyrohyoid ligament (arrowheads), the preepiglottic fat (*), and the hypoechoic epiglottic cartilage (solid arrows).

Posterior to the paraglottis, identify the piriform fossae, in particular, any mucosal thickening (this may be aided with the use of the Valsalva maneuver), the posterior cricoarytenoid muscle, and the inferior constrictor (thyropharyngeus) (Figs 2b, 2c, 4c).

Inferiorly, assess the cricoid cartilage, the proximal tracheal rings, and the layers of the cervical esophagus, which are usually well visualized on the left.

Fourth and Fifth (Right and Left Longitudinal) Sweeps

Finally, perform right and left longitudinal sweeps from posterior to anterior. These sweeps begin in the coronal plane, overlying the most posterior aspect of the thyroid lamina, and finish anteriorly in the midline sagittal plane (Movie 5).

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Movie 5. Cine images from laryngeal US show the right longitudinal sweep.

In the posterior aspect of the sweep, visualize the arytenoid cartilage. In particular, the superior aspect (apex), the base, and the concave surface (the fovea for the origin of the thyroarytenoid muscle), are visible parallel deep to the thyroarytenoid muscle (Fig 5a). While sweeping anteriorly, also note clear views of the superior extension of the hypoechoic thyroarytenoid muscle surrounded by the hyperechoic fat of the supraglottis (Fig 5a5c).

The laryngeal ventricles are best demonstrated in the middle part of this longitudinal sweep, cranial to the true cords. Visualization of the laryngeal ventricle may be aided by a Valsalva maneuver (Fig 5b, 5c). The symmetry of the true vocal cords can be compared for evidence of atrophy (Fig 6; Movie 6) or tumor by using a dual-screen projection on the US machine. The cricothyroid artery (branch of the superior thyroid artery of the external carotid artery) may sometimes be identified inferiorly, where it perforates the cricothyroid membrane (Fig 5c). The preepiglottic space and its relationship with the thin thyrohyoid membrane, the overlying strap muscles, and the deeper epiglottis are best identified more superiorly in the midline longitudinal plane, as are the lingual tonsil and tongue base (Fig 5d).

Right vocal cord palsy. US images show a comparison of the right and                         left sides, and illustrations (right) show the corresponding anatomic                         orientation. (a) Paramedian transverse plane US images at the level of the                         inferior thyroid lamina (dashed line) show atrophy and fat replacement of                         the right thyroarytenoid and vocalis muscles (solid arrow) when compared                         with a vocal cord of normal volume on the left side (dashed arrow). Note the                         arytenoid cartilage (+). (b) Sagittal US images show a similar                         appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a                         normal vocal cord (dashed arrow), and secondary enlargement of the right                         laryngeal ventricle (circle). (c) Transverse paramedian plane US image                         through the cricoid cartilage also shows atrophy of the right posterior                         cricoarytenoid muscle compared with the left (arrows).

Figure 6a. Right vocal cord palsy. US images show a comparison of the right and left sides, and illustrations (right) show the corresponding anatomic orientation. (a) Paramedian transverse plane US images at the level of the inferior thyroid lamina (dashed line) show atrophy and fat replacement of the right thyroarytenoid and vocalis muscles (solid arrow) when compared with a vocal cord of normal volume on the left side (dashed arrow). Note the arytenoid cartilage (+). (b) Sagittal US images show a similar appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a normal vocal cord (dashed arrow), and secondary enlargement of the right laryngeal ventricle (circle). (c) Transverse paramedian plane US image through the cricoid cartilage also shows atrophy of the right posterior cricoarytenoid muscle compared with the left (arrows).

Right vocal cord palsy. US images show a comparison of the right and                         left sides, and illustrations (right) show the corresponding anatomic                         orientation. (a) Paramedian transverse plane US images at the level of the                         inferior thyroid lamina (dashed line) show atrophy and fat replacement of                         the right thyroarytenoid and vocalis muscles (solid arrow) when compared                         with a vocal cord of normal volume on the left side (dashed arrow). Note the                         arytenoid cartilage (+). (b) Sagittal US images show a similar                         appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a                         normal vocal cord (dashed arrow), and secondary enlargement of the right                         laryngeal ventricle (circle). (c) Transverse paramedian plane US image                         through the cricoid cartilage also shows atrophy of the right posterior                         cricoarytenoid muscle compared with the left (arrows).

Figure 6b. Right vocal cord palsy. US images show a comparison of the right and left sides, and illustrations (right) show the corresponding anatomic orientation. (a) Paramedian transverse plane US images at the level of the inferior thyroid lamina (dashed line) show atrophy and fat replacement of the right thyroarytenoid and vocalis muscles (solid arrow) when compared with a vocal cord of normal volume on the left side (dashed arrow). Note the arytenoid cartilage (+). (b) Sagittal US images show a similar appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a normal vocal cord (dashed arrow), and secondary enlargement of the right laryngeal ventricle (circle). (c) Transverse paramedian plane US image through the cricoid cartilage also shows atrophy of the right posterior cricoarytenoid muscle compared with the left (arrows).

Right vocal cord palsy. US images show a comparison of the right and                         left sides, and illustrations (right) show the corresponding anatomic                         orientation. (a) Paramedian transverse plane US images at the level of the                         inferior thyroid lamina (dashed line) show atrophy and fat replacement of                         the right thyroarytenoid and vocalis muscles (solid arrow) when compared                         with a vocal cord of normal volume on the left side (dashed arrow). Note the                         arytenoid cartilage (+). (b) Sagittal US images show a similar                         appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a                         normal vocal cord (dashed arrow), and secondary enlargement of the right                         laryngeal ventricle (circle). (c) Transverse paramedian plane US image                         through the cricoid cartilage also shows atrophy of the right posterior                         cricoarytenoid muscle compared with the left (arrows).

Figure 6c. Right vocal cord palsy. US images show a comparison of the right and left sides, and illustrations (right) show the corresponding anatomic orientation. (a) Paramedian transverse plane US images at the level of the inferior thyroid lamina (dashed line) show atrophy and fat replacement of the right thyroarytenoid and vocalis muscles (solid arrow) when compared with a vocal cord of normal volume on the left side (dashed arrow). Note the arytenoid cartilage (+). (b) Sagittal US images show a similar appearance, with atrophy of the right thyroarytenoid muscle (solid arrow), a normal vocal cord (dashed arrow), and secondary enlargement of the right laryngeal ventricle (circle). (c) Transverse paramedian plane US image through the cricoid cartilage also shows atrophy of the right posterior cricoarytenoid muscle compared with the left (arrows).

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Movie 6. Cine images from laryngeal US show vocal cord palsy.

Laryngeal US for Evaluation of Laryngeal Cancer

Laryngeal cancer is a malignant neoplasm of the head and neck and is the 20th most common cancer in both Europe and the United States (18,19). Pretherapeutic staging is intimately related to disease-free and overall survival (4). Accurate pretherapeutic staging is essential in treatment planning and in the selection of the best therapy for each patient, the choice of which includes endoscopic laser resection, radiation therapy, voice-preserving partial laryngectomy, and total laryngectomy (3,10).

Currently, laryngoscopy combined with cross-sectional imaging (CT and/or MRI) is the routine method for the diagnosis and pretherapeutic staging of laryngeal cancer. Imaging is used to assess the submucosal extent of disease and the invasion of the preepiglottic and paraglottic fat of the supraglottic space, the cartilage, and the extralaryngeal space (3,5). Although CT and MRI are highly sensitive for the detection of intralaryngeal spread to pre-and paraglottic fat and the subglottic space, the specificity of these techniques tends to be low mainly because peritumoral inflammation is difficult to distinguish from tumoral involvement (8,15). The benefit of the high sensitivity and negative predictive value of MRI for cartilage invasion is overshadowed by the low specificity and low positive predictive value of MRI (2022). Although new MRI diagnostic criteria have gone some way to overcome this, recent data indicate that specificity for both CT and MRI remain low, at 88% and 81%, respectively, making decisions regarding cartilage invasion problematic (21), which makes detection problematic. This raises concerns because subtle invasion through the outer cortex of the cartilage and/or into the soft tissues beyond the larynx increases the tumor stage to T4, for which total laryngectomy may be indicated (7). Moreover, tumoral invasion of the cartilage predicts a high likelihood of radiation therapy failure (15,23,24).

US can be a useful adjunct to pretherapeutic staging in laryngeal carcinoma (35,10). Not only can US, because of its high resolution, allow confirmation of the absence of cartilaginous invasion (Fig 7), but it can also augment the diagnosis of submucosal laryngeal cancer extension and help in identification of subtle extralaryngeal extension that is suspected or not visible at CT or MRI (Figs 810).

The presence of prelaryngeal nodes (delphian nodes), an important route of lymphatic dissemination in laryngeal cancer, can be seen more easily with US than with CT and MRI, where differentiation from the strap muscles might be difficult (Fig 10).

Right paramedian transverse plane US image through the supraglottis shows                     a bulky tumor (T) but a smooth border (arrow) between the tumor and the                     overlying preserved nonossified thyroid cartilage (dashed line), which is in                     keeping with the absence of cartilage erosion in the T3 tumor (compare with Fig                     8).

Figure 7. Right paramedian transverse plane US image through the supraglottis shows a bulky tumor (T) but a smooth border (arrow) between the tumor and the overlying preserved nonossified thyroid cartilage (dashed line), which is in keeping with the absence of cartilage erosion in the T3 tumor (compare with Fig 8).

T4a tumor. Axial contrast material–enhanced CT image through the                     right supraglottis (a) and equivalent right paramedian transverse plane US image                     (b) show the sclerotic right thyroid lamina (arrow in a, dashed line in b), but                     no definite extralaryngeal tumor can be identified, because tumor and muscle                     show similar attenuation. The tumor (T) is clearly visible on the US image (b)                     and shows subtle extralaryngeal extension through a small thyroid cartilage                     erosion (dashed arrow in b). The tumor was staged as T4a, and laryngectomy was                     required .

Figure 8a. T4a tumor. Axial contrast material–enhanced CT image through the right supraglottis (a) and equivalent right paramedian transverse plane US image (b) show the sclerotic right thyroid lamina (arrow in a, dashed line in b), but no definite extralaryngeal tumor can be identified, because tumor and muscle show similar attenuation. The tumor (T) is clearly visible on the US image (b) and shows subtle extralaryngeal extension through a small thyroid cartilage erosion (dashed arrow in b). The tumor was staged as T4a, and laryngectomy was required .

T4a tumor. Axial contrast material–enhanced CT image through the                     right supraglottis (a) and equivalent right paramedian transverse plane US image                     (b) show the sclerotic right thyroid lamina (arrow in a, dashed line in b), but                     no definite extralaryngeal tumor can be identified, because tumor and muscle                     show similar attenuation. The tumor (T) is clearly visible on the US image (b)                     and shows subtle extralaryngeal extension through a small thyroid cartilage                     erosion (dashed arrow in b). The tumor was staged as T4a, and laryngectomy was                     required .

Figure 8b. T4a tumor. Axial contrast material–enhanced CT image through the right supraglottis (a) and equivalent right paramedian transverse plane US image (b) show the sclerotic right thyroid lamina (arrow in a, dashed line in b), but no definite extralaryngeal tumor can be identified, because tumor and muscle show similar attenuation. The tumor (T) is clearly visible on the US image (b) and shows subtle extralaryngeal extension through a small thyroid cartilage erosion (dashed arrow in b). The tumor was staged as T4a, and laryngectomy was required .

Tumor extension. Magnified axial T2-weighted MR image (a) and equivalent                     magnified transverse right paramedian US image (b) through the cricothyroid                     region show a subtle tumor extension through the cricothyroid membrane (long                     arrow in a), but a protrusion of anterior tumor extension is clearly shown on                     the US image (long arrow in b). Cricoid cartilage (*) and air in the lumen                     (short arrow) can also be seen on both images.

Figure 9a. Tumor extension. Magnified axial T2-weighted MR image (a) and equivalent magnified transverse right paramedian US image (b) through the cricothyroid region show a subtle tumor extension through the cricothyroid membrane (long arrow in a), but a protrusion of anterior tumor extension is clearly shown on the US image (long arrow in b). Cricoid cartilage (*) and air in the lumen (short arrow) can also be seen on both images.

Tumor extension. Magnified axial T2-weighted MR image (a) and equivalent                     magnified transverse right paramedian US image (b) through the cricothyroid                     region show a subtle tumor extension through the cricothyroid membrane (long                     arrow in a), but a protrusion of anterior tumor extension is clearly shown on                     the US image (long arrow in b). Cricoid cartilage (*) and air in the lumen                     (short arrow) can also be seen on both images.

Figure 9b. Tumor extension. Magnified axial T2-weighted MR image (a) and equivalent magnified transverse right paramedian US image (b) through the cricothyroid region show a subtle tumor extension through the cricothyroid membrane (long arrow in a), but a protrusion of anterior tumor extension is clearly shown on the US image (long arrow in b). Cricoid cartilage (*) and air in the lumen (short arrow) can also be seen on both images.

Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image                     obtained through the larynx with intravenous contrast agent administration (a),                     photograph of the pathologic sample (b), transverse US image (c), and more                     inferior transverse US image (d) through the cricothyroid region show that it is                     difficult to know whether the nonossified right thyroid lamina is invaded in a                     (arrow in a), but tumor extension is clearly visible in c (arrow in c) through                     both cortices of the anterior right thyroid lamina (dashed lines in c), a                     finding that was confirmed at histopathologic evaluation (b). In addition, two                     small prelaryngeal (delphian) nodes (* in d) are visible in the                     cricothyroid region on the US image in d that were not visible on the CT image.                     Markers (+) in c and d are for measurement of the nodes. Air lining the                     anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of                     Andrew McQueen, FRCR.)

Figure 10a. Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image obtained through the larynx with intravenous contrast agent administration (a), photograph of the pathologic sample (b), transverse US image (c), and more inferior transverse US image (d) through the cricothyroid region show that it is difficult to know whether the nonossified right thyroid lamina is invaded in a (arrow in a), but tumor extension is clearly visible in c (arrow in c) through both cortices of the anterior right thyroid lamina (dashed lines in c), a finding that was confirmed at histopathologic evaluation (b). In addition, two small prelaryngeal (delphian) nodes (* in d) are visible in the cricothyroid region on the US image in d that were not visible on the CT image. Markers (+) in c and d are for measurement of the nodes. Air lining the anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of Andrew McQueen, FRCR.)

Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image                     obtained through the larynx with intravenous contrast agent administration (a),                     photograph of the pathologic sample (b), transverse US image (c), and more                     inferior transverse US image (d) through the cricothyroid region show that it is                     difficult to know whether the nonossified right thyroid lamina is invaded in a                     (arrow in a), but tumor extension is clearly visible in c (arrow in c) through                     both cortices of the anterior right thyroid lamina (dashed lines in c), a                     finding that was confirmed at histopathologic evaluation (b). In addition, two                     small prelaryngeal (delphian) nodes (* in d) are visible in the                     cricothyroid region on the US image in d that were not visible on the CT image.                     Markers (+) in c and d are for measurement of the nodes. Air lining the                     anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of                     Andrew McQueen, FRCR.)

Figure 10b. Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image obtained through the larynx with intravenous contrast agent administration (a), photograph of the pathologic sample (b), transverse US image (c), and more inferior transverse US image (d) through the cricothyroid region show that it is difficult to know whether the nonossified right thyroid lamina is invaded in a (arrow in a), but tumor extension is clearly visible in c (arrow in c) through both cortices of the anterior right thyroid lamina (dashed lines in c), a finding that was confirmed at histopathologic evaluation (b). In addition, two small prelaryngeal (delphian) nodes (* in d) are visible in the cricothyroid region on the US image in d that were not visible on the CT image. Markers (+) in c and d are for measurement of the nodes. Air lining the anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of Andrew McQueen, FRCR.)

Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image                     obtained through the larynx with intravenous contrast agent administration (a),                     photograph of the pathologic sample (b), transverse US image (c), and more                     inferior transverse US image (d) through the cricothyroid region show that it is                     difficult to know whether the nonossified right thyroid lamina is invaded in a                     (arrow in a), but tumor extension is clearly visible in c (arrow in c) through                     both cortices of the anterior right thyroid lamina (dashed lines in c), a                     finding that was confirmed at histopathologic evaluation (b). In addition, two                     small prelaryngeal (delphian) nodes (* in d) are visible in the                     cricothyroid region on the US image in d that were not visible on the CT image.                     Markers (+) in c and d are for measurement of the nodes. Air lining the                     anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of                     Andrew McQueen, FRCR.)

Figure 10c. Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image obtained through the larynx with intravenous contrast agent administration (a), photograph of the pathologic sample (b), transverse US image (c), and more inferior transverse US image (d) through the cricothyroid region show that it is difficult to know whether the nonossified right thyroid lamina is invaded in a (arrow in a), but tumor extension is clearly visible in c (arrow in c) through both cortices of the anterior right thyroid lamina (dashed lines in c), a finding that was confirmed at histopathologic evaluation (b). In addition, two small prelaryngeal (delphian) nodes (* in d) are visible in the cricothyroid region on the US image in d that were not visible on the CT image. Markers (+) in c and d are for measurement of the nodes. Air lining the anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of Andrew McQueen, FRCR.)

Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image                     obtained through the larynx with intravenous contrast agent administration (a),                     photograph of the pathologic sample (b), transverse US image (c), and more                     inferior transverse US image (d) through the cricothyroid region show that it is                     difficult to know whether the nonossified right thyroid lamina is invaded in a                     (arrow in a), but tumor extension is clearly visible in c (arrow in c) through                     both cortices of the anterior right thyroid lamina (dashed lines in c), a                     finding that was confirmed at histopathologic evaluation (b). In addition, two                     small prelaryngeal (delphian) nodes (* in d) are visible in the                     cricothyroid region on the US image in d that were not visible on the CT image.                     Markers (+) in c and d are for measurement of the nodes. Air lining the                     anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of                     Andrew McQueen, FRCR.)

Figure 10d. Tumor extension and prelaryngeal nodes. Axial contrast-enhanced CT image obtained through the larynx with intravenous contrast agent administration (a), photograph of the pathologic sample (b), transverse US image (c), and more inferior transverse US image (d) through the cricothyroid region show that it is difficult to know whether the nonossified right thyroid lamina is invaded in a (arrow in a), but tumor extension is clearly visible in c (arrow in c) through both cortices of the anterior right thyroid lamina (dashed lines in c), a finding that was confirmed at histopathologic evaluation (b). In addition, two small prelaryngeal (delphian) nodes (* in d) are visible in the cricothyroid region on the US image in d that were not visible on the CT image. Markers (+) in c and d are for measurement of the nodes. Air lining the anterior wall of the subglottis (arrow in d) is visible. (Figure courtesy of Andrew McQueen, FRCR.)

The literature thus far has revealed US to have high sensitivity, but more importantly, high specificity for the assessment of cartilaginous tumoral invasion (sensitivity, 66.6%–87.5%; specificity, 92%–97.9% [4,10]). Subtle cartilage invasion is seen as the disappearance of the inner cartilaginous cortex.

Preservation of the thin hyperechoic line of residual paraglottic fat between the hypoechoic tumor and the thyroid lamina and a smooth border between the two indicate the absence of cartilage involvement (Figs 5a, 5b, 7).
Tumoral extension through the cartilage is present when the inner and outer cortex are destroyed by the hypoechoic lesion (Figs 8, 10).

US can allow identification of tumoral extension into the preepiglottic and paraglottic spaces, which increases the stage from a supraglottic tumor to T3 disease (7).

The hyperechoic preepiglottic fat is identified at US as bounded anteriorly by the thyrohyoid membrane and posteriorly by the hypoechoic epiglottis (Figs 1c, 5d). The preepiglottic fat communicates laterally with the similar hyperechoic fat in the paraglottic space (Fig 1c, 1d).
At US, supraglottic laryngeal carcinoma can be clearly delineated because it appears hypoechoic in comparison with the hyperechoic fat of the adjacent paraglottic and preepiglottic spaces and with the surrounding air of the larynx (Figs 710, Movies 710).
The paraglottic space shows a degree of mobility during respiration, whereas the inner perichondrium of the thyroid cartilage is immobile (4). Xia et al (4) showed that when complete or partial immobility of the paraglottic space was visualized, US could allow diagnosis of tumoral involvement of this area with the same sensitivity as that for CT (95.5% vs 100%, respectively) but with higher specificity (94.9% vs 67%, respectively).

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Movie 7. Cine images from laryngeal US in a patient with supraglottic carcinoma (right side of the tumor larger than left side) show the left paramedian sweep with no extralaryngeal extension. Note also the nondistended left internal laryngocele.

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Movie 8. Cine images from laryngeal US in a patient with supraglottic carcinoma (right side larger than left side) show the midline transverse sweep with no extralaryngeal extension.

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Movie 9. Cine images from laryngeal US show the right paramedian axial sweep of a right supraglottic tumor.

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Movie 10. Cine images from laryngeal US in a patient with supraglottic carcinoma (right side larger than left side) show the right paramedian transverse sweep with no extralaryngeal extension.

US may be used to delineate the tumoral involvement of other key anatomic sites including the arytenoids, the vocal cords, and the anterior commissure.

Involvement of the anterior commissure may sometimes be more clearly identified with US than with cross-sectional imaging, where the anterior commissure may be difficult to delineate. At US, a hypoechoic mass can be visualized in this region.
The involvement of the anterior commissure is common in glottic tumors and is associated with early invasion of the thyroid cartilage, the preepiglottic space, and the subglottic region as well as with tumor recurrence after radiation therapy (25,26) (Fig 11). In one study (3), the accuracy rate for detection of anterior commissure involvement was 88.9% for US and 86.1% for CT (3). Glottic tumors themselves can be better appreciated with US. Tumors as small as 6 mm that were not visible with MRI have been detected with US (10). Although it is usually not possible to visualize the posterolateral subglottis with US because of air interference, its anterolateral aspects may be clearly visualized with this technique (4,10).

Changes to the epiglottis in a patient who underwent radiation therapy for                     laryngeal carcinoma. Midline transverse plane US image (a) and axial CT image                     through the supraglottis obtained with intravenous contrast agent administration                     (b) show smooth diffuse thickening of the epiglottis and the adjacent                     aryepiglottic folds (arrows) that are in keeping with expected postradiation                     therapy change (compare with Fig 1c, 1d).

Figure 11a. Changes to the epiglottis in a patient who underwent radiation therapy for laryngeal carcinoma. Midline transverse plane US image (a) and axial CT image through the supraglottis obtained with intravenous contrast agent administration (b) show smooth diffuse thickening of the epiglottis and the adjacent aryepiglottic folds (arrows) that are in keeping with expected postradiation therapy change (compare with Fig 1c, 1d).

Changes to the epiglottis in a patient who underwent radiation therapy for                     laryngeal carcinoma. Midline transverse plane US image (a) and axial CT image                     through the supraglottis obtained with intravenous contrast agent administration                     (b) show smooth diffuse thickening of the epiglottis and the adjacent                     aryepiglottic folds (arrows) that are in keeping with expected postradiation                     therapy change (compare with Fig 1c, 1d).

Figure 11b. Changes to the epiglottis in a patient who underwent radiation therapy for laryngeal carcinoma. Midline transverse plane US image (a) and axial CT image through the supraglottis obtained with intravenous contrast agent administration (b) show smooth diffuse thickening of the epiglottis and the adjacent aryepiglottic folds (arrows) that are in keeping with expected postradiation therapy change (compare with Fig 1c, 1d).

A further benefit of US in pretherapeutic staging of laryngeal tumors is in the identification of subtle extralaryngeal extension that is suspected or not visible with CT or MRI. Subtle invasion through the thyroid notch and thyrohyoid membrane, and more inferiorly, through the cricothyroid membrane can be clearly depicted (Fig 9). These findings increase the staging to T4, for which laryngectomy is usually required (7). Subtle tumoral extension superiorly into the lingual tonsil and tongue base region, which affects the clinical management, can be identified with the sagittal US sweep (the 6.5–8-MHz sector and the linear probe are often required to assess this region).

A diagnostic advantage of US over cross-sectional imaging is the ability to perform targeted biopsies in areas that may be otherwise inaccessible. This is particularly the case for patients who cannot undergo general anesthesia or for whom there is clinical suspicion for submucosal recurrence and in cases of difficult localization or a previous negative biopsy. Biopsy is usually performed transcutaneously through the thyrohyoid membrane. Intraoperative localization and confirmation of resection may be performed when there are small focal areas that are suspicious for submucosal recurrence, such as in neuroendocrine neoplasia.

A combination of MRI, CT, and US increases diagnostic confidence and accuracy in staging the primary laryngeal tumor and in assessment of the nodal status. Furthermore, the preepiglottic and paraglottic spaces are well imaged with US. The subglottic region, which is necessary for accurate staging and cannot be assessed with endoscopic examination, is readily imaged with US. In addition, US allows assessment of vocal cord movement in real time to diagnose vocal cord fixation, which is a sign of stage T3 cancer (7) and is particularly important when large supraglottic tumors may impair laryngoscopic visualization of the vocal cords (10).

Uses of Laryngeal US in Evaluation of Benign Laryngeal Disease

A variety of benign abnormalities are readily imaged with high-resolution US, and in some cases, these abnormalities are better appreciated at US than at cross-sectional imaging (5).

Vallecular cysts can be easily identified in the vallecula as hypoechoic or anechoic swellings. Frequently they are incidental findings, but large cysts can cause the sensation of a lump in the throat, and this area should always be reviewed when US is performed in this group of patients (Fig 12).

Vallecular cyst. (a) Midline transverse plane US image at the level of the                     vallecula shows a left vallecular cyst (arrow) arising from the anterior wall.                     The anterior wall of the right vallecula (*) is visualized. (b)                     Illustration shows the anatomic orientation of a.

Figure 12a. Vallecular cyst. (a) Midline transverse plane US image at the level of the vallecula shows a left vallecular cyst (arrow) arising from the anterior wall. The anterior wall of the right vallecula (*) is visualized. (b) Illustration shows the anatomic orientation of a.

Vallecular cyst. (a) Midline transverse plane US image at the level of the                     vallecula shows a left vallecular cyst (arrow) arising from the anterior wall.                     The anterior wall of the right vallecula (*) is visualized. (b)                     Illustration shows the anatomic orientation of a.

Figure 12b. Vallecular cyst. (a) Midline transverse plane US image at the level of the vallecula shows a left vallecular cyst (arrow) arising from the anterior wall. The anterior wall of the right vallecula (*) is visualized. (b) Illustration shows the anatomic orientation of a.

Thyroglossal cysts are usually diagnosed when neck US is performed for a recent lump in the midline anterior cervical region. The cyst lies in or just behind the strap muscles. Its content may be echogenic, making it pseudosolid and difficult to differentiate from a solid lesion. The use of color or power Doppler US or the application of gentle pressure on the probe and noting the movement of the internal echoes are helpful in these situations. It is important to assess the regularity of the lesion; its superior extent, including its relationship to the hyoid bone and any suprahyoid extension; and in rare cases, whether there are solid components that may be suggestive of a cystic papillary lesion. These features can also help to determine if the lesion is a dermoid cyst (27,28). Generally, a track of thyroglossal duct remnant connects the cyst to the pyramidal lobe of the thyroid (Fig 13). The assessment of the small suprahyoid tract and the pyramidal lobe is more clearly visualized with US than with other modalities and should be the initial imaging modality of choice.

Thyroglossal cyst. Midline sagittal plane US images show the thyrohyoid                     region (a) and tongue base (b), with illustrations (right) of the corresponding                     anatomic orientation. (a) US image shows a thin-walled thyroglossal cyst                     (*) extending superiorly, superficial to the thyroid lamina (dashed line)                     up to the hyoid bone (H). (b) US image shows a midline suprahyoid component                     (*) within the tongue base. The dorsal surface of the tongue (solid arrows)                     and the epiglottis (dashed arrow) are seen.

Figure 13a. Thyroglossal cyst. Midline sagittal plane US images show the thyrohyoid region (a) and tongue base (b), with illustrations (right) of the corresponding anatomic orientation. (a) US image shows a thin-walled thyroglossal cyst (*) extending superiorly, superficial to the thyroid lamina (dashed line) up to the hyoid bone (H). (b) US image shows a midline suprahyoid component (*) within the tongue base. The dorsal surface of the tongue (solid arrows) and the epiglottis (dashed arrow) are seen.

Thyroglossal cyst. Midline sagittal plane US images show the thyrohyoid                     region (a) and tongue base (b), with illustrations (right) of the corresponding                     anatomic orientation. (a) US image shows a thin-walled thyroglossal cyst                     (*) extending superiorly, superficial to the thyroid lamina (dashed line)                     up to the hyoid bone (H). (b) US image shows a midline suprahyoid component                     (*) within the tongue base. The dorsal surface of the tongue (solid arrows)                     and the epiglottis (dashed arrow) are seen.

Figure 13b. Thyroglossal cyst. Midline sagittal plane US images show the thyrohyoid region (a) and tongue base (b), with illustrations (right) of the corresponding anatomic orientation. (a) US image shows a thin-walled thyroglossal cyst (*) extending superiorly, superficial to the thyroid lamina (dashed line) up to the hyoid bone (H). (b) US image shows a midline suprahyoid component (*) within the tongue base. The dorsal surface of the tongue (solid arrows) and the epiglottis (dashed arrow) are seen.

Laryngoceles and laryngeal mucoceles are readily imaged with US. The presence of air or fluid is seen in the paraglottic space, extending from the laryngeal ventricle. It is important to exclude an underlying obstructing tumor involving the laryngeal ventricle (Fig 14).

Bilateral laryngeal mucoceles seen at US. Illustrations (right) show the                     corresponding anatomic orientation. (a) Midline transverse plane US image at the                     level of the thyroid notch shows two fluid-filled laryngeal mucoceles. The one                     on the left (solid arrow) is larger than the one on the right (dashed arrow) in                     both paraglottic spaces. (b) Left longitudinal plane US image shows the superior                     extension of the left laryngeal mucocele (long arrow) up to but not through the                     thyrohyoid membrane (short arrows). Note the thyroid cartilage (dashed line). An                     obstructing laryngeal ventricular tumor should always be excluded as the cause                     of a laryngocele.

Figure 14a. Bilateral laryngeal mucoceles seen at US. Illustrations (right) show the corresponding anatomic orientation. (a) Midline transverse plane US image at the level of the thyroid notch shows two fluid-filled laryngeal mucoceles. The one on the left (solid arrow) is larger than the one on the right (dashed arrow) in both paraglottic spaces. (b) Left longitudinal plane US image shows the superior extension of the left laryngeal mucocele (long arrow) up to but not through the thyrohyoid membrane (short arrows). Note the thyroid cartilage (dashed line). An obstructing laryngeal ventricular tumor should always be excluded as the cause of a laryngocele.

Bilateral laryngeal mucoceles seen at US. Illustrations (right) show the                     corresponding anatomic orientation. (a) Midline transverse plane US image at the                     level of the thyroid notch shows two fluid-filled laryngeal mucoceles. The one                     on the left (solid arrow) is larger than the one on the right (dashed arrow) in                     both paraglottic spaces. (b) Left longitudinal plane US image shows the superior                     extension of the left laryngeal mucocele (long arrow) up to but not through the                     thyrohyoid membrane (short arrows). Note the thyroid cartilage (dashed line). An                     obstructing laryngeal ventricular tumor should always be excluded as the cause                     of a laryngocele.

Figure 14b. Bilateral laryngeal mucoceles seen at US. Illustrations (right) show the corresponding anatomic orientation. (a) Midline transverse plane US image at the level of the thyroid notch shows two fluid-filled laryngeal mucoceles. The one on the left (solid arrow) is larger than the one on the right (dashed arrow) in both paraglottic spaces. (b) Left longitudinal plane US image shows the superior extension of the left laryngeal mucocele (long arrow) up to but not through the thyrohyoid membrane (short arrows). Note the thyroid cartilage (dashed line). An obstructing laryngeal ventricular tumor should always be excluded as the cause of a laryngocele.

Benign abnormalities of the vocal cords (ie, cysts, nodules, and polyps) are also visible at US (Fig 15). However, sometimes the free margins of the posterior vocal cords cannot be clearly visualized because of the air–soft tissue interface, impeding their assessment (5).

Right vocal cord cyst. (a) Right paramedian transverse plane US image                     through the inferior thyroid lamina (dashed line) shows a right vocal cord cyst                     (arrow), true and false vocal folds (*), and arytenoid cartilage (+).                     (b) Illustration shows the anatomic orientation.

Figure 15a. Right vocal cord cyst. (a) Right paramedian transverse plane US image through the inferior thyroid lamina (dashed line) shows a right vocal cord cyst (arrow), true and false vocal folds (*), and arytenoid cartilage (+). (b) Illustration shows the anatomic orientation.

Right vocal cord cyst. (a) Right paramedian transverse plane US image                     through the inferior thyroid lamina (dashed line) shows a right vocal cord cyst                     (arrow), true and false vocal folds (*), and arytenoid cartilage (+).                     (b) Illustration shows the anatomic orientation.

Figure 15b. Right vocal cord cyst. (a) Right paramedian transverse plane US image through the inferior thyroid lamina (dashed line) shows a right vocal cord cyst (arrow), true and false vocal folds (*), and arytenoid cartilage (+). (b) Illustration shows the anatomic orientation.

The US assessment of vocal cord palsy in real time is useful in patients who are unable to tolerate laryngoscopy, when laryngoscopy is not available, or when a supraglottic mass prevents the laryngoscopic assessment of the glottis. Asking the patient to breathe in and hold their breath, adducting the vocal cords, and then breathe out is a better method for assessment of vocal cord movement at US than phonation, because there is less laryngeal movement with US. In recent years, the utility of US in pre- and postoperative vocal cord checks in patients undergoing thyroidectomy has been recognized (29). To date, there have been mixed findings when correlating US-based diagnoses with standard laryngoscopic findings (sensitivity, 33%–100% [29] and specificity, 97%–100% [30]). Laryngeal US is performed largely by endocrine surgeons in these circumstances. The high negative predictive value (97%–99% [17]) of laryngeal US in pre- and postthyroidectomy vocal cord checks may indicate the utility of laryngeal US as a screening tool, with laryngoscopy for confirmation in positive cases (31).

Vocal cord palsy may be indicated when US shows atrophy and absence of movement of the vocal cord, posterior cricoarytenoid atrophy, anteromedial deviation of the arytenoid, or enlargement of the ventricle and piriform sinus (Fig 6).

The assessment of the position (measured in relation to the anterior aspect of the cricoid ring or numbered tracheal rings) and/or complications of tracheal stents such as a stay suture abscess may be performed with US, which allows ready identification and position checking of the sutures used to fix the tracheal stent (Fig 16). The suture is visualized as a curvilinear echogenic line extending from the skin through the anterior wall of the trachea. It is important to check with the clinician about the expected proximal extent of the stent, because its position is variable, depending on the extent of the tracheal stenosis.

Stent. Transverse midline (a) and sagittal midline (b) US images through                     the proximal cervical trachea and cricoid cartilage. Note the top (proximal                     aspect) of the stent (solid arrow) within the proximal cervical trachea just                     posterior to the anterior wall (dashed arrow). The distance between the anterior                     aspect of the cricoid (curved outline in b) and the proximal stent can be                     measured.

Figure 16a. Stent. Transverse midline (a) and sagittal midline (b) US images through the proximal cervical trachea and cricoid cartilage. Note the top (proximal aspect) of the stent (solid arrow) within the proximal cervical trachea just posterior to the anterior wall (dashed arrow). The distance between the anterior aspect of the cricoid (curved outline in b) and the proximal stent can be measured.

Stent. Transverse midline (a) and sagittal midline (b) US images through                     the proximal cervical trachea and cricoid cartilage. Note the top (proximal                     aspect) of the stent (solid arrow) within the proximal cervical trachea just                     posterior to the anterior wall (dashed arrow). The distance between the anterior                     aspect of the cricoid (curved outline in b) and the proximal stent can be                     measured.

Figure 16b. Stent. Transverse midline (a) and sagittal midline (b) US images through the proximal cervical trachea and cricoid cartilage. Note the top (proximal aspect) of the stent (solid arrow) within the proximal cervical trachea just posterior to the anterior wall (dashed arrow). The distance between the anterior aspect of the cricoid (curved outline in b) and the proximal stent can be measured.

Laryngeal US is also valuable for prediction of the likelihood of postextubation stridor in intubated adults and children. Assessment of the difference in the width of the column of air that passes through the vocal cords while the endotracheal tube is inflated and deflated showed that patients who went on to develop postextubation stridor had a significantly narrowed air column width (32,33). However, low sensitivity and positive predictive value in one study (34) show that these findings should be used as a guide and interpreted with caution.

Conclusion

Most of the laryngeal constituents are readily identified with high-resolution US, even in a heavily calcified larynx, because thyrohyoid and cricothyroid membranes are suitable for the transmission of the ultrasound beams.

US provides high-resolution images and is a powerful, usually complementary, imaging modality for the diagnosis of malignant and benign laryngeal abnormalities. It also allows identification of laryngeal anatomy (eg, the vocalis muscle, detailed arytenoid cartilage anatomy, and the thyrohyoid ligament) that is not clearly identifiable with MRI or CT. It is readily available, noninvasive, and radiation free and offers real-time imaging with video acquisition and higher resolution than does cross-sectional imaging. It is also suitable for many patients with laryngeal diseases who have difficulty keeping still during CT or MRI acquisition.

High-resolution US can be a useful tool (in combination with cross-sectional imaging) to allow more accurate and confident staging of laryngeal carcinomas, particularly in the assessment of subtle extralaryngeal extension, which affects clinical management.

For this journal-based SA-CME activity, the authors, editor, and reviewers have disclosed no relevant relationships.

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Article History

Received: May 20 2019
Revision requested: July 24 2019
Revision received: Sept 30 2019
Accepted: Oct 15 2019
Published online: May 04 2020
Published in print: May 2020